A little-known planet about 111 light years away could be a "scaled-up version of Earth" and may be able to host alien life, according to a study.

The exoplanet known as K2-18b has been described as being a potential 'Super-Earth' - a large rocky planet with the potential to support life.

Researchers at the University of Toronto in Canada made the discovery by scouring data collected by the European Southern Observatory(ESO).

They also discovered a new planet in the same solar system. Both planets orbit K2-18, a red-dwarf star located about 111 light-years away in the constellation Leo.

"Being able to measure the mass and density of K2-18b was tremendous, but to discover a new exoplanet was lucky and equally exciting," said Ryan Cloutier, a PhD student at the University of Toronto.

When the planet K2-18b was first discovered in 2015, it was found to be orbiting within the star's habitable zone, making it an ideal candidate to have liquid surface water, a key element in harbouring conditions for life as we know it.

"It was not a eureka moment because we still had to go through a checklist of things to do in order to verify the data," said Cloutier, lead author of the study published in the journal Astronomy and Astrophysics.

"Once all the boxes were checked it sunk in that, wow, this actually is a planet," he said.

The dataset used by Cloutier and other researchers came from the High Accuracy Radial Velocity Planet Searcher (HARPS) using the ESO's 3.6-metre telescope at La Silla Observatory, in Chile.

In order to figure out whether K2-18b was a scaled-up version of Earth (mostly rock), or a scaled-down version of Neptune (mostly gas), researchers had to first figure out the planet's mass, using radial velocity measurements taken with HARPS.

After using a machine-learning approach to figure out the mass measurement, Cloutier and his team were able to determine the planet is either a mostly rocky planet with a small gaseous atmosphere - like Earth, but bigger - or a mostly water planet with a thick layer of ice on top of it.

"With the current data, we cannot distinguish between those two possibilities," Cloutier said.

"But with the James Webb Space Telescope (JWST), we can probe the atmosphere and see whether it has an extensive atmosphere or it is a planet covered in water," he said.

"K2-18b is now one of the best targets for atmospheric study, it is going to the near top of the list," Rene Doyon, from Universite de Montreal Institute in Canada, added.

It was while looking through the data of K2-18b that Cloutier noticed something unusual.

In addition to a signal occurring every 39 days from the rotation of K2-18, and one taking place every 33 days from the orbit of K2-18b, he noticed a different signal occurring every nine days.